R2 is a constant. When I set R2 smaller than 33000, I can always got a numerical solution of u[y]. However when R2 gets very large,i.e. 40000, mathematica just doesn't work at all. I mean there is no solution given for the third differential equation.

Can anybody tell me how to solve this problem? I will be more than appreciated.

Please post a fully self contained non-working example that one can copy/paste and run to show the problem including any numerical values used.
–
NasserMar 11 '14 at 0:57

Thanks for your reply. I have posted the full code.
–
zeoMar 11 '14 at 1:07

Can you reduce the size of your example, and indicate where exactly and what goes wrong? It'll save people a lot of time and might get you an answer. All I see now is that at some point the kernel crashes, but I didn't take the time to find out at which step. I think you can do this yourself and let us know.
–
SzabolcsMar 11 '14 at 1:32

That said, a kernel crash indicates a bug, so can you report this to support at wolfram.com ?
–
SzabolcsMar 11 '14 at 1:34

Mathematica is a registered trademark of Wolfram Research, Inc. While the mark is used herein with the limited permission of Wolfram Research, Stack Exchange and this site disclaim all affiliation therewith.